I want to check whether the generic class type is an Array:
func test<T>() -> Wrapper<T> {
let isArray = T.self is Array<Any>
...
}
But it warns
Cast from 'T.type' to unrelated type 'Array' always fails
How can I solve this problem?
added: I've uploaded my codes to Gist. https://gist.github.com/nallwhy/6dca541a2d1d468e0be03c97add384de
What I want to do is to parse json response according to it's an array of model or just one model.
As commentator @Holex says, you can use Any. Combine it with Mirror and you could, for example, do something like this:
func isItACollection(_ any: Any) -> [String : Any.Type]? {
let m = Mirror(reflecting: any)
switch m.displayStyle {
case .some(.collection):
print("Collection, \(m.children.count) elements \(m.subjectType)")
var types: [String: Any.Type] = [:]
for (_, t) in m.children {
types["\(type(of: t))"] = type(of: t)
}
return types
default: // Others are .Struct, .Class, .Enum
print("Not a collection")
return nil
}
}
func test(_ a: Any) -> String {
switch isItACollection(a) {
case .some(let X):
return "The argument is an array of \(X)"
default:
return "The argument is not an array"
}
}
test([1, 2, 3]) // The argument is an array of ["Int": Swift.Int]
test([1, 2, "3"]) // The argument is an array of ["Int": Swift.Int, "String": Swift.String]
test(["1", "2", "3"]) // The argument is an array of ["String": Swift.String]
test(Set<String>()) // The argument is not an array
test([1: 2, 3: 4]) // The argument is not an array
test((1, 2, 3)) // The argument is not an array
test(3) // The argument is not an array
test("3") // The argument is not an array
test(NSObject()) // The argument is not an array
test(NSArray(array:[1, 2, 3])) // The argument is an array of ["_SwiftTypePreservingNSNumber": _SwiftTypePreservingNSNumber]
Try out define an array marker protocol. Refer to this answer.
protocol AnyTypeOfArray {}
extension Array: AnyTypeOfArray {}
extension NSArray: AnyTypeOfArray {}
func isArray<T>(type: T.Type) -> Bool {
return T.self is AnyTypeOfArray.Type
}
print(isArray(type: [String].self)) // true
print(isArray(type: String.self)) // false
You are not passing any argument, so there is no type and a generic function does not make sense. Either remove the generic type:
func() {}
or, if you want to pass an argument:
let array = ["test", "test"]
func test<T>(argument: T) {
let isArray = argument is Array<Any>
print(isArray)
}
test(argument: array)
Prints: true
T be found out? What do you expect the method to return as T?
Any could do the job as well – and who does return the true value? because it is defintely not your method.